For the last 11 years, tickets for the touring rock music festival have steadily climbed in price.

"It's business as usual, except it's free. We want to encourage new music and new talent," said the singer's wife and manager Sharon Osbourne.

The Black Sabbath singer will headline the 25-date tour, which will begin on 7 July in Los Angeles.

In the past, fans have been asked to pay up to $150 (£76) for Ozzfest tickets.

Gary Bongiovanni, editor of the concert trade publication Pollstar, said this is the first time admission has been free for a US touring festival.

"It's a phenomenal idea," he said.

Retirement denial

Tour sponsors will pick up the cost of any overheads and bands will perform for free on multiple outdoor stages.

Fans can obtain tickets through websites set up for the event.

Sharon Osbourne denied rumours that her husband plans to retire after the festival.

"He's been touring 30, 35 years, and he's done very well, and it's time to give something back," she told the Associated Press.

"If he goes out one summer of his life and he doesn't get paid, big deal."

He has nearly finished recording a new solo album, which is due out the last week of June.